CVE-2021-20986 in PROFINET IO Device
Summary
by MITRE • 02/16/2021
A Denial of Service vulnerability was found in Hilscher PROFINET IO Device V3 in versions prior to V3.14.0.7. This may lead to unexpected loss of cyclic communication or interruption of acyclic communication.
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Analysis
by VulDB Data Team • 03/02/2021
The vulnerability identified as CVE-2021-20986 represents a critical denial of service weakness within Hilscher PROFINET IO Device V3 software versions prior to V3.14.0.7. This flaw specifically impacts industrial automation environments where PROFINET communication protocols are utilized for real-time control systems. The affected device operates within the industrial internet of things ecosystem, where communication reliability is paramount for operational continuity and safety. PROFINET IO devices serve as essential components in manufacturing and process control systems, making this vulnerability particularly concerning for critical infrastructure sectors. The vulnerability stems from insufficient handling of communication protocols that govern both cyclic and acyclic data transmission within the PROFINET framework, creating potential points of failure that could disrupt operational workflows.
The technical root cause of this vulnerability involves improper state management and error handling within the PROFINET IO Device firmware. When subjected to specific communication patterns or malformed data packets, the device fails to maintain stable communication channels for both cyclic and acyclic data flows. Cyclic communication, which operates on fixed time intervals for real-time control signals, and acyclic communication, which handles configuration and diagnostic data, both become susceptible to interruption. This represents a CWE-400 vulnerability category related to uncontrolled resource consumption, where the device's communication handling logic does not adequately validate incoming data or maintain proper state transitions. The flaw allows attackers to potentially exploit communication patterns that cause the device to reset or enter an unstable state, effectively creating a denial of service condition that impacts the entire industrial control network.
The operational impact of CVE-2021-20986 extends beyond simple communication disruption to potentially compromise entire industrial processes. When cyclic communication is interrupted, real-time control systems may lose synchronization with critical actuators and sensors, leading to production halts or unsafe operational conditions. Acyclic communication disruptions can prevent system diagnostics, configuration updates, and maintenance activities that are essential for operational reliability. This vulnerability directly impacts the availability and integrity of industrial control systems, creating risks that align with the industrial control system security framework defined by NIST and IEC 62443 standards. The attack surface for this vulnerability includes any network segment where PROFINET IO devices are deployed, particularly in manufacturing environments, oil and gas facilities, and power generation plants where continuous operation is critical.
Mitigation strategies for this vulnerability require immediate firmware updates to V3.14.0.7 or later versions provided by Hilscher. Network segmentation and access controls should be implemented to limit exposure of PROFINET IO devices to untrusted networks, reducing potential attack vectors. Monitoring systems should be deployed to detect anomalous communication patterns that may indicate exploitation attempts, particularly focusing on cyclic communication interruptions and acyclic data flow disruptions. Security controls should be aligned with the MITRE ATT&CK framework, specifically targeting the execution and privilege escalation phases that could lead to device compromise. Organizations should conduct comprehensive vulnerability assessments of their industrial control networks to identify all affected devices and implement layered defensive measures including intrusion detection systems, network monitoring tools, and regular security audits. The vulnerability also highlights the importance of maintaining updated industrial security protocols and adhering to the principle of least privilege for network access to industrial control systems.